The present invention relates to a system for providing heat transfer between a smooth coldsheet and a flowing fluid. More specifically, a gap is formed between the coldsheet to be cooled and a facesheet containing many fluid supply and return nozzles. The fluid is fed to the supply nozzles, travels a short distance within the gap adjacent to the facesheet and exits via return nozzles. The flow cross section and flow density facilitate heat transfer at a moderate flow rate and low fluid pressure. The invention also has application for chemical transfer such as etching or plating printed circuit boards and for transfer through a semi-permeable membrane.
The term "intense heat transfer" is defined as the transfer of maximum heat when taking into consideration the following: the temperature difference between the coldsheet and incoming fluid, the area of the coldsheet, the thermal conductivity and specific heat of the fluid, and the use of a small fluid pressure drop.
The prior art contains many relevant structures useful for intense heat transfer. For instance, a theoretical discussion of cooling considerations is presented in an article in the IEEE Electron Devices Letters entitled "High Performance Heat Sinking For VSLI" by D. B. Tuckerman and R. F. Pease vol. EDL-2, No. 5, May 1981. The described arrangement requires many fine grooves and fins to be fabricated in a coldplate of highly thermal conductive material in order to achieve intense heat transfer. The fine fins and grooves are critical for achieving intense heat transfer. When relatively coarse fins and grooves are substituted, the heat transfer is less intense.
The technique of multiple jet impingement is described in the article "Impinging Jet Flow Heat and Mass Transfer" by Holfer Martin in Advances in Heat Transfer, Vol 13 (1977). The technique relied upon uses multiple nozzles and a relatively high fluid pressure to emit multiple jets of fluid with relatively high speed which impinges on a coldplate. When relatively small pressure is used the heat transfer is less intense. Also, as noted in the Martin article, cooling a large area by means of an array of jets results in degradation of the heat transfer near the center of the array.
Other prior art techniques increase heat transfer between a surface and adjacent flowing fluid by disrupting the boundary layer. One such example is loops of wire along the inner surface of a tube in a heat exchanger. Another example is a screen of wires along a surface which transfers heat to a flowing liquid. A stirrer refers to a structure which acts or is located near a surface, and promotes stirring, mixing, or turbulence in a flowing liquid. The stirrer may be integral with the surface, or may be an adjacent but distinct structure. Fins generally do not cause stirring, particularly in the regime of small or intermediate Reynolds' s number. A turbulator promotes turbulence, particularly at large Reynolds' number. The term stirrer generally includes "turbulator" but generally excludes fins. In general, a stirrer uses a large pressure gradient to achieve intense convection.
The prior art fails to teach how to achieve intense and uniform heat transfer from a large smooth sheet to a flowing fluid by means of a combination of low fluid pressure and medium fluid flow density.